I think most of the blame goes to Campbell and Mrazek, but some of it has to do with Keefe as well. If your goaltending department as a whole is struggling, maybe they can dedicate the next 2 week segment or whatever to more lockdown defense, with the following suggestions:
-Decide on your defense pairs based on a puck carrier/stopper logic with the personnel you have. And keep them together for the full 2 weeks and stabilize.
-Transition stuff before we're in a defensive posture:
-Stricter rules for puck management: don't leave pucks on those touch passes in the neutral zone.
-Yellow light for activating the point man offensively. Sometimes it's safer to concede the zone entry and defend the neutral zone than trying to jam a body down the sidewall only to have the opposition chip it out for an odd man rush with speed.
-Just put the D men on tighter rails positionally. There was one give and go play where Marner ended up taking a point shot with Rielly trying to tip the puck in the slot. Or when Lyubushkin started on the right point, crossed over, took a pass and somehow migrated into the left wing corner. If they're getting this scrambled up offensively, it doesn't put the Leafs on a firm footing when the game shifts back into their own zone.
-Dermott is not allowed to make head fakes, spin-o-rama's little shimmy plays when exiting his zone and fake shots.
Defensive posture:
-So often the goalies seem confused from where the shots are taken. Maybe there's some some work to be done establishing some ground rules how they want to see shots and what the defensive body positioning should be trying to when protecting the slot, what kind of rebounds the goalie wants to kick out and where.
-Protect the slot better. Lately it looks like a fire drill, but just calm it down, have a more structured box out and go back to the more defined roles with your static pairings.